To answer your queries I will need to first explain a bit about what makes humans special.

While I was on my recent tour of Earth I was shown a video of a human hunting a kudu (a local herbivorous quadruped). Kudus are much faster than humans, so the kudu easily sprinted away, but they also lack the humans' endurance, so whenever it had to stop and rest the human would close the distance. Eventually after the better part of a local day of this sprinting and too short rests while the human jogged along behind it the kudu collapsed from exhaustion, and the human simply walked up to it and finished it off with a small knife he carried for that purpose.

The humans I was with quite correctly thought that this video demonstrated what made humans special; where they where mistaken was in what attribute of humanity demonstrated in the video was actually so unusual (I didn't even fully get it myself until much later).

Most of the humans with me focused on the running; over a long-enough distance, and in a hot-enough environment (the video was filmed in one of the hotter parts of their homeworld) humans can beat pretty much anything else from their home planet. But while impressive, there's several other sentient species that can compete with them, and even a couple that could easily outrun them.

One or two humans suggested that it was stubbornness; surely the ability to keep going for a whole day even though for much of the run it must look pretty futile--as if the kudu wasn't actually getting any tireder--is unusual? But in reality humans are little more than above average in this regard.

(In fact my own species, the Huxaar, have a fairly solid claim to being the "Kings-of-Stubbornness"; I once saw a warrior who had lost nearly 90% of his body mass to a plasma bolt not only survive and continue to fight, while outnumbered, but he ended up winning, and with modern medicine he made a full recovery physically (two of his redundant brains where completely destroyed and the third somewhat damaged, which sadly resulting in minor memory loss))

No, the humans completely missed the important point, and since you probably have only a vague idea of what a human is like physically, and no idea at all of what a kudu is like I imagine you haven't realised what it is either. An adult kudu weighs somewhere between five and seven Kuy [Approximately 177-247kg], and has sharp hooves, and horns of around 30-40 Bulew [Approximately 38-50cm], while the human in question would have been lucky to hit two Kuy [Approximately 70kg], wore no armour, and as I mentioned only had a small knife to supplement his few natural weapons, which, on humans, range from the poor to the laughable.

Despite this absurd match-up the kudu was the one to run away. Why? Because the human acted as if he could win, and the kudu believed him. I couldn't understand why this was happening at the time, so I started looking into more human hunting techniques. This special form of deception is sufficient common among humans as to warrant it's own name, "bluffing" in the language of the dominant culture.

As well as several more standard techniques (it seems nearly every carnivorous sentient comes up with the idea of sneaking up on your prey and stabbing it with a pointy stick at some point), there where several more examples of the same sort of thing, such as groups of humans in their prehistory scaring herds of mammoths (which can literally be a hundred times the size of a human) so much that they'd rather run off a cliff than hang around and fight the humans, or more recent examples of humans waiting until a group of lions (a much bigger and stronger non-sentient predator) had killed a prey animal, and then chasing the lions away from their food.

For a more mundane example take the "bullwhip", a bull is a creature that can easily weigh 30+ Kuy [Approximately 1060+kg], has horns and hooves like the kudu, and a reputation for aggressive stubbornness. Yet a bullwhip is barely better than a human's natural weapons in a fight; it's real advantage is that it's noisy. Yes, when having to deal with an animal fifteen times their size they think a noisemaker is a reasonable piece of equipment. (Apparently the bulls do occasionally realise the absurdity, which can end tragically, but such events must be rare, otherwise becoming a farmer would simply be a rather elaborate form of suicide for humans)

You might get the impression from the above that humans only bluff dumb animals, that would be a mistake, they will happily bluff each other, or even aliens as I learnt to my chagrin when I discovered the game of "poker".

[A detailed, and somewhat dry, explanation of the rules of poker was originally provided here, but it doubled the word-count of this letter, and the translator felt that that would be unnecessary for the intended human audience of this translation.]

I trust you can see how such a game could be of interest, particularly to more statistically inclined individuals, when played straight, but that's not how the humans play. Bluffing is seen as a core part of the game. A common strategy is to bet far more than your cards would warrant in the hope that other players that might actually have better hands will lose their nerve and fold. The social skills to deceive the other players or spot their deceptions are seen as the real skill of good players.

I initially discovered the game when I was travelling through a small town in their southern hemisphere. I noticed an ad for a "Poker Tournament" on one of the local sporting clubs. When I expressed an interest in finding out more my guide kindly took me to the club and let me observe the games.

After observing for several minutes I had a feel for the rules and realised that many of the human players didn't seem to really grasp the odds involved, so I rather over-confidently joined a game expecting to do reasonably well.

One of the humans who was playing with me, and, I must admit, thoroughly thrashing me, was generous enough to inform me after about ten hands that it was obvious that Huxaarians where ill-suited for poker, and that I should withdraw now before I lost any more money. He was even kind enough to offer to give me back half the money he had won off me.

(I later found out that he was an very good poker player, so much so that several of the other humans donated to a "float" for him--winnings to be spent on beer for club members. He had realised I was completely incapable of detecting a bluff by the third hand, and I think he was feeling guilty about winning the equivalent of nearly half a year of local wages in the next seven hands)

What's this digression about human betting games got to do with your query? Well, remember what I said above about Huxaarian stubbornness, and complete inability to give up? Even it's obvious to everyone that we couldn't possibly win?

That is how the Huxaarian Empire became a vassal state of the South Maitland Bowls Club.

As for your second query: I assume that you're smart enough to see why I can't say if the humans are serious when they claim to be able to beat the Glibelian Fleets easily if you invade.

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Emperor Halak IIVassal Emperor of HuxaarSpecial Adviser to the Imperial Board of the South Maitland Bowls Clubetc.

Written from the Imperial Palace on Huxaar Prime

Letter to the Glibelian Ambassador dated 12th of Bilu in the 7th year of Emperor Halak II [Approximately 11th of May 2032 AD]

I can easily understand why the destruction of the cream of the Glibelian Fleets by the new 3rd Provincial Fleet (Flagship: The Golden Bluff) is distressing for your leadership.

I've reread my last letter, and it appears that I failed to mention that sometimes a good bluffer will pretend to be weaker than he actually is. "Oops, my bad"; as I'm assured that the young humans say.

PS: My condolences on the loss of nearly 20% of your offworld holdings. I understand that the loss of the pleasure palaces on Rilo III has been particularly frustrating to your court members.

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Emperor Halak IIVassal Emperor of HuxaarSpecial Adviser to the Imperial Board of the South Maitland Bowls Clubetc.

Written from the Green Moon Pleasure Palace on New South Maitland (formerly Rilo III)